A purely analog line-following robot using the LM324N quad op-amp as voltage comparators to process IR sensor input and directly drive motors — zero microcontroller required for the primary control loop. Arduino Nano provides backup digital control for edge-case recovery.
The LM324N comparator outputs directly modulate the H-bridge motor driver — no ADC sampling, no software delays.
IR Sensor Array (3 channels) ├──────┬──────┬──────┤ │ L │ C │ R │ ▼ ▼ ▼ ┌──────────────────────┐ │ LM324N │ │ Quad Comparator │ │ Vref ┤ + - ├ Vin │ │ ├──────┤ │ │ Ch1 │ Ch2 │ Ch3 │ └──┬────┴──┬───┴──┬────┘ │ │ │ ▼ ▼ ▼ ┌──────────────────────┐ │ L293D H-Bridge │ │ Motor Driver │ │ M_L M_R │ └──────────────────────┘ ┌─── Arduino Nano ───┐ │ Backup Digital │ │ Control (edge │ │ case recovery) │ └─────────────────────┘
Quad op-amp package provides 4 comparator channels in a single DIP-14 IC. Eliminates ADC quantization delays for near-instantaneous sensor→motor response.
Primary control path is pure analog: IR voltage → comparator threshold → motor drive. Zero processor overhead, zero sampling jitter — the fastest possible control loop.
Digital MCU monitors the analog path and takes over during edge cases like sharp turns, intersections, or line-loss scenarios where simple threshold comparison fails.
Potentiometer-adjustable Vref on each comparator channel enables field calibration for different surface colors and lighting conditions.
| Component | Part | Role |
|---|---|---|
| Comparator | LM324N | Quad op-amp as voltage comparators |
| Backup MCU | Arduino Nano | Edge-case digital control |
| Motor Driver | L293D H-Bridge | Dual DC motor control |
| Sensors | IR Reflectance Array | Line detection (3 channels) |
| Tuning | Trimpots | Vref threshold adjustment |
| Power | 7.4V LiPo | Dual-rail supply via regulator |